Problem Description: All XML processing within the TYPO3 CMS are vulnerable to XEE processing. This can lead to load internal and/or external (file) content within an XML structure. Furthermore it is possible to inject arbitrary files for an XML Denial of Service attack. For more information on that topic see https://www.owasp.org/index.php/XML_External_Entity_(XXE)_Processing.

Solution: Update to TYPO3 versions 6.2.19 or 7.6.4 that fix the problem described.

Important Note: Systems using a PHP version with libxml2 >= 2.9 should be protected by default. Since version 2.9 the library changed its behavior to disallow external entity processing by default.

Credits: Thanks to security team member Marcus Krause who discovered and reported the issue.